The present invention relates to spread-spectrum communications and more particularly to a method and apparatus for enhancing communications by using phased array principles for increasing signal-to-noise ratio for a spread spectrum signal with multipath arriving at a receiver.
Achieving sufficient signal strength when a received signal comes from two paths is a problem when communicating with spread-spectrum modulation in a multipath environment. The received signal from the two paths may have phase cancellation, yielding no reception, or reception with an unacceptable error rate.
Phased arrays, as is well known in the art, require N antenna elements for distinguishing up to Nxe2x88x921 signals arriving at the phased array from different paths or directions. This concept of spatial diversity is well developed in antenna theory.
A spread spectrum base station has a set of phased array antennas for receiving a spread spectrum signal containing a plurality of channels. The base station outputs timed version of the received signal. Each timed version is associated with a respective one out of said set of phased array antennas. A plurality of despread signals is produced by despreading each timed version of the received signal using chip code sequences associated with the plurality of channels and combining the despread signals as a combined despread signal. A magnitude of the combined despread signal for obtaining a present a prior magnitude is determined. The present magnitude is compared with the prior magnitude. A delay associated with the timed versions in response to the comparison is adjusted, so antenna beams associated with the set of phased array antennas are steered towards components of the spread spectrum signal with a highest combined magnitude.